1. Field of the Invention
This invention pertains to a heat exchanger used for an automobile air conditioner.
2. Description of the Related Art
Conventional parallel flow type heat exchangers include a multi-layer structure of alternately stacked tube and fin members and header pipes connected to opposite ends of the tube members. The front surface of these heat exchangers generally defines a rectangular configuration. (See, for example, Japanese Kokai Patent No. 63-34466.)
However, to improve aerodynamic characteristics, there is a trend toward streamlining automobile hoods, and less top to bottom space is provided in front of the engine chamber. Therefore, there is often insufficient space provided in the vicinity of the lower portions of the heat exchanger which is positioned in front of the engine chamber, since head lights and pipe members also occupy and require space. If the size of the heat exchanger is reduced accordingly to facilitate positioning, a problem arises in that the heat exchanging capacity lowers as the front surface dimensions of the heat exchanger are reduced.
To cope with this problem, heat exchangers have been formed into shapes other than rectangles to enable the heat exchanger to be positioned without lowering heat exchanging capacity. Such heat exchangers are disclosed in Japanese Kokai Patent Publication Utility Model H1-161106 and Japanese Kokai Patent Publication H2-37287.
In the former publication (Kokai Patent Publication Utility Model H1-161106), a heat exchanger is formed in a desired configuration by dividing each header pipe into multiple pipe members and combining the members with tubes of different sizes.
In the latter publication (Kokai Patent Publication H2-37287), a heat exchanger is formed in a desired configuration by eliminating the four corners. This is done by bending both ends of the header pipe and making the length of the tubes corresponding to the bent portion of the header pipes shorter than that of the other tubes.
However, in the former constitution, since the header pipe is divided into multiple pipe members, and the tubes are supported only by the fins between them, the heat exchanger has insufficient structural strength. Therefore, the heat exchanger is susceptible to being deformed when it is installed in an automobile, which has been a problem.
In the latter constitution, bending a header pipe is a difficult task and a heat exchanger having a desired configuration cannot always be attained. Furthermore, the use of bent header pipes requires the provision of tubes of a variety of lengths, which is a problem in terms of cost, and therefore, is not practical.
Japanese Kokai Patent Publication Utility Model No. 63-74989 discloses a heat exchanger having a different front surface shape, in which one end of each of the multiple tubes in a stack is aligned and connected to one of the header tanks, and the other end of each of the tubes grouped according to size is connected to each of the multiple header tanks, which are divided along their length. Japanese Kokai Patent Publication Utility Model No. H2-127957 also discloses a heat exchanger, in which the front surface is formed in a different shape by the same method, and in which blind caps installed on the ends of each of the divided multiple header tanks are integrally connected with one another to reinforce the divided header tanks.
With these heat exchangers, a problem arises since the tubes are supported by jigs facing in toward the tube stack when the heat exchangers are soldered in an ordinary process, the ends of the divided header tanks connected to the ends of the shorter tubes are pressed against the middle point along the length of the longer tubes, resulting in deformation of the longer tubes.